Memory devices are widely used to store information in various electronic devices such as computers, wireless communication devices, cameras, digital displays, and the like. Information is stored by programming different states of a memory device. For example, binary devices have two states, often denoted by a logic “1” or a logic “0.” In other systems, more than two states may be stored. To access the stored information, a component of the electronic device may read, or sense, the stored state in the memory device. To store information, a component of the electronic device may write, or program, the state in the memory device.
Multiple types of memory devices exist, including magnetic hard disks, random access memory (RAM), dynamic RAM (DRAM), synchronous dynamic RAM (SDRAM), ferroelectric RAM (FeRAM), magnetic RAM (MRAM), resistive RAM (RRAM), read only memory (ROM), flash memory, phase change memory (PCM), and others. Memory devices may be volatile or non-volatile. Non-volatile memory, e.g., FeRAM, may maintain their stored logic state for extended periods of time even in the absence of an external power source. Volatile memory devices, e.g., DRAM, may lose their stored state over time unless they are periodically refreshed by an external power source. Improving memory devices may include increasing memory cell density, increasing read/write speeds, increasing reliability, increasing data retention, reducing power consumption, or reducing manufacturing costs, among other metrics.
In some memory architectures, a memory cell may include a storage element and a selection component. The selection component may be activated by applying a voltage across the selection component that activates the selection component allowing current to flow through the memory cell. The voltage necessary to activate the selection component may be referred to as a threshold voltage. The threshold voltage of the selection component may affect the voltage applied across the storage element; the voltage across storage element may equal the voltage across the memory cell minus the voltage across the selection component. In some examples, the threshold voltage may vary from one selection component to another (e.g., due to local temperatures, aging, process variations, etc.), causing a voltage applied across the storage element (e.g., a read or write voltage) to vary as well. In some examples, the threshold voltage of a selection component itself may vary over time.